\documentclass{article}

\usepackage{pgfplots}

\pgfplotsset{compat=1.14}

\begin{document}

\begin{tikzpicture}
	\pgfmathsetseed{1}
	\begin{axis}[colormap name=viridis,colorbar]
	% this here must not affect the contour:
	\addplot3[scatter, only marks, samples=4] {-120- rnd * 50};

	\addplot3[contour filled={number=5, }] {x^2*y};
	
	% this here must not affect the contour:
	\addplot3[scatter, only marks, samples=4] {120+ rnd * 50};
	\end{axis}
\end{tikzpicture}
\end{document}

